This paper stems from the first sampled and representative survey carried out on the Yellow Vests movement in the French region of Occitania. While scientific literature mainly explores the drivers of internal—social and ideological—cohesion in social movements, our study sheds light on the internal diversity of the Yellow Vests' mobilisation. Our findings reveal the unprecedented scale of the movement in relation to the French population. They confirm and document its social and political heterogeneity. We confirm that the working and lower middle classes are over-represented in the movement. But our study also highlights the diversity of the coalition formed by the Yellow Vests who are, in fact, fairly representative of the French working and middle classes in all their diversity, including the upper-middle class. Only the upper classes are not part of the movement. In part two, we explore the cleavages that unite the Yellow Vests as well as those that divide them. While they are cohesive on economic issues and their strong rejection of political elites, the Yellow Vests are highly divided on identity and cultural issues. The results allow us to shed light on the forms and dynamics of the movement. Indeed, the variety of ideological and social profiles, as well as grievances, is reflected in the partially differentiated spatial distribution of the participants across the various protest sites. Our analysis also offers keys to understanding the process by which demands were generated and framed, the reasons for the mistrust shown towards would-be spokespeople and the difficulty in translating the movement into the political and electoral arena. Our study underlines the processual nature of any social movement and prompts us not to overestimate the unity, uniformity, and similarity of its participants, since many Yellow Vests probably rallied not so much together as alongside each other.